Tilt-rotor aircraft are aircraft that hover like helicopters with their rotors turning in the horizontal plane (axis of rotation in the vertical plane), and tilt their rotors in the vertical plane to fly like propeller driven aircraft. The Bell™-Boeing™ V-22 and Bell™/Agusta™ 609 are examples of prior art tilt-rotor aircraft.
Tilt-wing aircraft have rotors or propellers installed on their wings, which can tilt from wing-borne propeller-driven flight to helicopter-like flight in which the propellers are more or less in the horizontal position. The Vought™/Hiller™/Ryan™ XC-142A is an example of a prior art tilt-wing aircraft.
The development of aircraft precision automatic flight control and of unmanned vertical take-off and landing (VTOL) aircraft provide for automated control of precision hover flight with no or minimal pilot input. Modern rotorcraft equipped with such systems can now routinely perform precision hover over a specified geographical point and therefore accurately place a cargo suspended below the rotorcraft. Such operation can either use the vertical motion of the rotorcraft or use a winch to lower the cargo to the desired position. The use of helicopters to perform short-range point-to-point external load pickup and delivery is referred to as aerial crane operations. Using helicopters for external load carriage over long distances is inefficient because of the drag of an external load and the inefficiency of conventional helicopter configurations in forward flight.
In most cases cargo aircraft, including cargo rotorcraft, have cabins or cargo holds that provide for internal carriage of cargo; such cargo holds often have a loading ramp that may further serve as a door to the cargo hold. The cargo hold and loading ramp arrangement provide for rapid roll-on and roll-off of wheeled and tracked vehicles, and for environmental protection of the cargo. Most importantly, the internal carriage of cargo provides a substantially lower air resistance (drag) in forward flight, as compared with cargo suspended below the rotorcraft. The lower drag allows for faster speed and increased range of the rotorcraft per available fuel amount. As used herein, any mention of “deliver”, “lowering” and “placing” should be interpreted as conceptually including pick-up and lifting of cargo.
In conventional operations, delivery of internally carried cargo is performed either by rolling-off or extraction after landing, or in fixed wing aircraft, by horizontal extraction in forward flight using a parachute. Such horizontal extraction is used on military cargo aircraft including for example the Lockheed-Martin™ C-130.
Both of these prior art cargo delivery methods can be problematic. The roll-off after landing method requires a landing area suitable for the aircraft landing, which may not be available in rugged terrain or delivery in urban or forested areas. Alternately, the in-flight horizontal extraction method often cannot provide the desired precision and soft placement of the cargo.
Thus, there is still a need for improved apparatus, systems and methods for placement of internally carried cargo.